How to insert an item into an array at a specific index (JavaScript)

You want the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert).

In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join()); // Jani,Hege,Stale,Kai Jim,Borge
arr.splice(2, 0, "Lene");
console.log(arr.join()); // Jani,Hege,Lene,Stale,Kai Jim,Borge

There is no support of such functionality in lodash : see issue.

If you still want it to look like done with lodash, then you can do it like this way.

fields = [{name: 'john'},
          {name: 'jane'},
          {name: 'saske'},
          {name: 'jake'},
          {name: 'baki'}
         ];

_.insert = function (arr, index, item) {
  arr.splice(index, 0, item);
};

_.insert(fields,2,{'name':'ace'});

console.log(fields);

That’s all about inserting an item at a specific index in an array using JavaScript., This post will discuss how to insert an item at a specific index in an array using JavaScript., The following code demonstrates how to use the splice() method to insert an item at the specified index in the array:, The splice solution modifies the original array. If you don’t want to change the original array, create a new array using the ES6 Spread operator with slicing.

The splice() method can be used to modify the array by removing or replacing existing elements and/or adding new elements in place.

The following code demonstrates how to use the splice() method to insert an item at the specified index in the array:

splice()

3. Using Array.prototype.push() function

To add elements at the end of an array, you can use the push() method.

push()

In JavaScript, it's not advisable to loop through an Array with a for-in loop, but it's better to use a for loop such as:

for(var i=0, len=myArray.length; i < len; i++){}

It's optimized as well ("caching" the array length). If you'd like to learn more, read my post on the subject.